1. Field of the Invention
The present invention relates to a substrate processing apparatus and a substrate processing method which process a substrate. Examples of the substrate to be processed include semiconductor wafers, substrates for liquid crystal display devices, substrates for plasma display devices, substrates for FED (Field Emission Display) devices, substrates for optical disks, substrates for magnetic disks, substrates for magneto-optical disks and substrates for photo masks.
2. Description of the Related Art
In semiconductor device manufacturing processes, the front surface of substrates such as semiconductor wafers is processed with processing liquid. Substrate processing apparatuses of a single substrate processing type, in which substrates are processed one by one, include a spin chuck arranged to rotate a substrate while holding the substrate thereon approximately horizontally and a nozzle arranged to supply processing liquid therethrough onto the front surface of the substrate rotated by the spin chuck.
In such substrate processing apparatuses of a single substrate processing type, chemical solution is supplied onto the substrate held on the spin chuck. Thereafter, rinse liquid is supplied onto the substrate. The chemical solution on the substrate is thus replaced with the rinse liquid. Thereafter, a spin drying step is performed to remove the rinse liquid on the substrate. In the spin drying step, the substrate undergoes a high-speed rotation so that the rinse liquid adhering to the substrate is spun off and removed (for drying).
In such a spin drying step, it may not be possible to sufficiently remove rinse liquid getting into a pattern formed on the substrate, which may result in poor drying. To resolve this problem, there has been proposed a technique in which organic solvent solution such as isopropyl alcohol (IPA) liquid is supplied onto the front surface of a substrate after rinse processing to replace rinse liquid getting into a pattern with the organic solvent solution and thereby to dry the front surface of the substrate, as described in Japanese Patent Application Publication No. 9-38595, for example.
In such a conventional spin drying step, two adjacent patterns may be attracted to each other to result in a pattern collapse. This is believed to be attributed in part to the surface tension of liquid existing between the two adjacent patterns. It is believed that since organic solvent such as IPA, if supplied onto the substrate before the spin drying step, having a lower surface tension, exists between the two adjacent patterns, the force attracting the patterns to each other is reduced and thus the patterns can be prevented from being collapsed.
Recently, however, fine and high-aspect-ratio patterns (convex patterns, linear patterns, etc.) are formed on the front surface of semiconductor substrates for higher integration. Such fine patterns are likely to be collapsed and, even if organic solvent may be supplied onto the substrate before the spin drying step, the fine patterns may not be sufficiently prevented from being collapsed.